14.2.2 Predefined Syntaxes

If you’re programming with Regex, you can set a pattern buffer’s
(see GNU Pattern Buffers)
syntax either to an arbitrary combination of syntax bits
(see Syntax Bits) or else to the configurations defined by Regex.
These configurations define the syntaxes used by certain
programs—GNU Emacs,
POSIX Awk,
traditional Awk,
Grep,
Egrep—in addition to syntaxes for POSIX basic and extended
regular expressions.